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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Hydro power flexibility for power systems with variable renewable energy sources: an IEA Task 25 collaboration: Hydro power flexibility for power systems

Hydro power is one of the most flexible sources of electricity production. Power systems with considerable amounts of flexible hydro power potentially offer easier integration of variable generation, e.g., wind and solar. However, there exist operational constraints to ensure mid-/long-term security of supply while keeping river flows and reservoirs levels within permitted limits. In order to properly assess the effective available hydro power flexibility and its value for storage, a detailed assessment of hydro power is essential. Due to the inherent uncertainty of the weather-dependent hydrological cycle, regulation constraints on the hydro system, and uncertainty of internal load as well as variable generation (wind and solar), this assessment is complex. Hence, it requires proper modeling of all the underlying interactions between hydro power and the power system, with a large share of other variable renewables. A summary of existing experience of wind integration in hydro-dominated power systems clearly points to strict simulation methodologies. Recommendations include requirements for techno-economic models to correctly assess strategies for hydro power and pumped storage dispatch. These models are based not only on seasonal water inflow variations but also on variable generation, and all these are in time horizons from very short term up to multiple years, depending on the studied system. Another important recommendation is to include a geographically detailed description of hydro power systems, rivers' flows, and reservoirs as well as grid topology and congestion.

13 HYDRO ENERGY↗
DOE OSTI2023

Fast Ramping Accelerator Dipole Models for Fermilab’s Booster Upgrade and Muon Collider

The future discoveries in the field of High Energy Physics are led by the development of new types of accelerators. Around the world, there are a lot of researchers that are studying some possible designs for the future accelerators and some of them are considering the use of alternating current inside the superconducting magnets in order to have better efficiency. The work described in this report tries to compare some superconducting magnets made of different materials and to understand which one of them can be considered for its better performance working in a variable magnetic field. For this goal, becomes really important to control the temperature of the coil, and, as visible in the next chapter, to relate this parameter to the frequency of the magnetic field, in order to find, as will be named, the critical frequency .

43 PARTICLE ACCELERATORS↗
DOE OSTI2016

Comparison of Measured and Numerically Simulated Turbulence Statistics in a Convective Boundary Layer Over Complex Terrain

High resolution numerical simulation can provide insight into important physical processes that occur within the planetary boundary layer (PBL). The present work employs large eddy simulation (LES) nested within the Weather Forecasting and Research (WRF) framework to simulate real conditions in the convective PBL over an area of complex terrain. A multiple nesting approach has been used to downsize the grid spacing size from 12.15 km (mesoscale) to 0.03 km (LES). To minimize artifacts in theWRF-LES solutions resulting from using an inappropriate grid spacing on the WRF-Meso domain, a careful selection of grid spacing has been conducted. The WRF-LES results have been evaluated with in situ and remote sensing observations collected during the US Department of Energy supported Columbia BasinWind Energy Study (CBWES). The comparison for the first and second order moments, turbulence spectrum, and probability density function (pdf) of wind speed show good agreement between the simulation and data. Furthermore, the WRF-LES variables show a great deal of variability in space and time caused by the complex topography in the LES domain. The WRF-LES results show that the flow structures, such as roll vortices and convective cells, over the domain vary depending on both the spatial location and time of the day. In addition to basic studies related to boundary-layer meteorology, results from these simulations can be used in other applications, such as studying the wind energy resources.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2017

Marginal Cost Pricing in a World without Perfect Competition: Implications for Electricity Markets with High Shares of Low Marginal Cost Resources

A common approach to regulating electricity is through auction-based competitive wholesale markets. The goal of this approach is to provide a reliable supply of power at the lowest reasonable cost to the consumer. This necessitates market structures and operating rules that ensure revenue sufficiency for all generators needed for resource adequacy purposes. Wholesale electricity markets employ marginal-cost pricing to provide cost-effective dispatch such that resources are compensated for their operational costs. However, marginal-cost pricing alone cannot guarantee cost recovery outside of perfect competition, and electricity markets have at least six attributes that preclude them from functioning as perfectly competitive markets. These attributes include market power, externalities, public good attributes, lack of storage, wholesale price caps, and ineffective demand curve. Until (and unless) these failures are ameliorated, some form of corrective action(s) will be necessary to improve market efficiency so that prices can correctly reflect the needed level of system reliability. Many of these options necessarily involve some form of administrative or out-of-market actions, such as scarcity pricing, capacity payments, bilateral or other out-of-market contracts, or some hybrid combination. A key focus with these options is to create a connection between the electricity market and long-term reliability/loss-of-load expectation targets, which are inherently disconnected in the native markets because of the aforementioned market failures. The addition of variable generation resources can exacerbate revenue sufficiency and resource adequacy concerns caused by these underlying market failures. Because variable generation resources have near-zero marginal costs, they effectively suppress energy prices and reduce the capacity factors of conventional generators through the merit-order effect in the simplest case of a convex market; non-convexities can also suppress prices.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2016

Data-driven parameterization of the generalized Langevin equation

Significance The generalized Langevin equation (GLE) provides a precise description of coarse-grained variable dynamics in reduced dimension models. However, computation of the memory kernel poses a major challenge to the practical use of the GLE. This paper presents a data-driven approach to compute the memory kernel, relying on a hierarchy of parameterized rational approximations in terms of the Laplace transform, which can be expanded to arbitrarily high order as necessary. This parameterization makes it convenient to represent the GLE via an extended stochastic model where the memory term is eliminated by properly introducing auxiliary variables. The present method is well-suited for constructing reduced models for nonequilibrium properties of complex systems such as biomolecules, chemical reaction networks, and climate simulations.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2016

Carbon Nanotube Chopped Fiber for Enhanced Properties in Additive Manufacturing

Nanocomp Technologies, Inc. is working with Oak Ridge National Laboratory to develop carbon nanotube (CNT) composite materials and evaluate their use in additive manufacturing (3D printing). The first phase demonstrated feasibility and improvements for carbon nanotube (CNT)- acrylonitrile butadiene styrene (ABS) composite filaments use in additive manufacturing, with potential future work centering on further improvements. By focusing the initial phase on standard processing methods (developed mainly for the incorporation of carbon fibers in ABS) and characterization techniques, a basis of knowledge for the incorporation of CNTs in ABS was learned. The ability to understand the various processing variables is critical to the successful development of these composites. From the degradation effects on ABS (caused by excessive temperatures), to the length of time the ABS is in the melt state, to the order of addition of constituents, and also to the many possible mixing approaches, a workable flow sequence that addresses each processing step is critical to the final material properties. Although this initial phase could not deal with each of these variables in-depth, a future study is recommended that will build on the lessons learned for this effort.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2014

COMPARISON OF PHOTOMETRIC VARIABILITY BEFORE AND AFTER STELLAR FLARES

The energy in the solar acoustic spectrum is known to be correlated with flares, but it is not known if the same is true for stellar flares. In order to answer this question, we have analyzed 73 flares in 39 solar-like stars. These flares were identified in the 854 solar-like stars observed by the Kepler spacecraft that have stellar parameters measured with asteroseismology. Though we were not able to identify a statistically significant enhancement of the energy in the high-frequency part of the post-flare acoustic spectra compared to the pre-flare spectra of these stars, we did identify a larger variability between the energy in the high-frequency part of the post- and pre-flare acoustic spectra compared to spectra taken at random times.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2022

Spatial Microbial Respiration Variations in the Hyporheic Zones Within the Columbia River Basin

Abstract While the hyporheic zone (HZ) accounts for a significant portion of whole stream CO 2 concentrations, HZ respiration modeling studies are lacking in quantifying their contributions to the total CO 2 at large watershed/basin scales. Quantifying the contribution of anaerobic respiration is also underappreciated. This study used a carbon‐nitrogen‐coupled river corridor model to quantify HZ aerobic and anaerobic respiration and determined the key factors controlling their spatial variability within the Columbia River Basin (CRB). The modeled respiration patterns showed high spatial variability. Among the nine sub‐basins composing the CRB, the Lower Columbia and the Willamette, which receive higher precipitation, had higher respiration. Medium‐sized rivers (fourth to sixth orders) produced the highest aerobic and anaerobic respiration among reaches of different sizes. At the basin scale, aerobic respiration is dominant, representing approximately 98.7% of the total respiration across the CRB. While most of the reaches were dominant with aerobic respiration, reaches in agricultural land showed a relatively higher anaerobic respiration (18%) ratio. A variable importance analysis showed that hyporheic exchange flux controlled most of the spatial variability of HZ respiration, dominating over other physical variables such as residence time, stream dissolved organic carbon (DOC), nitrate, and dissolved oxygen (DO). The influence of substrate concentration (DOC and DO) is larger in modeling anaerobic respiration than aerobic respiration. Future efforts will focus on improving the estimation of the HZ exchange flux and the implementation of spatially explicit parameterizations for the reactions of interest to reduce model uncertainty.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2013

Component and System Level Research of Variable Capacity Heat Pumps

With high cooling and heating efficiencies, variable capacity heat pumps are an emerging technology with the potential to substantially reduce the energy required for the heating and cooling of residential structures. In order for them to make an impact in this area, they must first be more widely accepted by the American consumer as an alternative to less expensive single speed systems. This acceptance, in large part, is based upon a greater understanding of how these systems perform in real world tests. To this end, this study will evaluate the energy consumption and efficiencies of four variable capacity heat pumps installed in two unoccupied research homes in Farragut, a suburb of Knoxville, Tennessee, one occupied home in downtown Knoxville, and one occupied home in Duluth, Georgia.

Munk, Jeffrey D.↗
DOE OSTI2016

THE B AND Be STATES OF THE STAR EM CEPHEUS

We present 11 yr of high-resolution, spectroscopic observations for the star EM Cep. EM Cep switches between B and Be star states, as revealed by the level of Hα emission, but spends most of its time in the B star state. EM Cep has been considered to be an eclipsing, near-contact binary of nearly equal-mass B stars in order to reproduce regular photometric variations; however, this model is problematic due to the lack of any observed Doppler shift in the spectrum. Our observations confirm that there are no apparent Doppler shifts in the wide spectral lines Hα and He i λ6678 in either the B or Be star states. The profiles of He i λ6678 typically exhibited a filled-in absorption core, but we detected weak emission in this line during the highest Be state. Given the lack of observed Doppler shifts, we model EM Cep as an isolated Be star with a variable circumstellar disk. We can reproduce the observed Hα emission profiles over the 11 yr period reasonably well with disk masses on the order of 3--10× 10{sup −11} M{sub ∗} in the Be state with the circumstellar disk seen at an inclination of 78° to the line of sight. From a disk ejection episode in 2014, we estimate a mass-loss rate of ≈3×10{sup −9} M{sub ⊙} yr{sup −1}. The derived disk density parameters are typical of those found for the classical Be stars. We therefore suggest that the EM Cep is a classical Be star and that its photometric variations are the result of β Cep or nonradial pulsations.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2015

Temperature dependence of contact and dipolar NMR chemical shifts in paramagnetic molecules

Using a recently proposed equation for NMR nuclear magnetic shielding for molecules with unpaired electrons [A. Soncini and W. Van den Heuvel, J. Chem. Phys. 138, 021103 (2013)], equations for the temperature (T) dependent isotropic shielding for multiplets with an effective spin S equal to 1/2, 1, 3/2, 2, and 5/2 in terms of electron paramagnetic resonance spin Hamiltonian parameters are derived and then expanded in powers of 1/T. One simplifying assumption used is that a matrix derived from the zero-field splitting (ZFS) tensor and the Zeeman coupling matrix (g-tensor) share the same principal axis system. The influence of the rhombic ZFS parameter E is only investigated for S = 1. Expressions for paramagnetic contact shielding (from the isotropic part of the hyperfine coupling matrix) and pseudo-contact or dipolar shielding (from the anisotropic part of the hyperfine coupling matrix) are considered separately. The leading order is always 1/T. A temperature dependence of the contact shielding as 1/T and of the dipolar shielding as 1/T{sup 2}, which is sometimes assumed in the assignment of paramagnetic chemical shifts, is shown to arise only if S ≥ 1 and zero-field splitting is appreciable, and only if the Zeeman coupling matrix is nearly isotropic (Δg = 0). In such situations, an assignment of contact versus dipolar shifts may be possible based only on linear and quadratic fits of measured variable-temperature chemical shifts versus 1/T. Numerical data are provided for nickelocene (S = 1). Even under the assumption of Δg = 0, a different leading order of contact and dipolar shifts in powers of 1/T is not obtained for S = 3/2. When Δg is not very small, dipolar and contact shifts both depend in leading order in 1/T in all cases, with sizable contributions in order 1/T{sup n} with n = 2 and higher.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Bayesian learning of orthogonal embeddings for multi-fidelity Gaussian Processes

Uncertainty propagation in complex engineering systems often poses significant computational challenges related to modeling and quantifying probability distributions of model outputs, as those emerge as the result of various sources of uncertainty that are inherent in the system under investigation. Gaussian Processes regression (GPs) is a robust meta-modeling technique that allows for fast model prediction and exploration of response surfaces. Multi-fidelity variations of GPs further leverage information from cheap and low fidelity model simulations in order to improve their predictive performance on the high fidelity model. In order to cope with the high volume of data required to train GPs in high dimensional design spaces, a common practice is to introduce latent design variables that are typically projections of the original input space to a lower dimensional subspace, and therefore substitute the problem of learning the initial high dimensional mapping, with that of training a GP on a low dimensional space. Here in this paper, we present a Bayesian approach to identify optimal transformations that map the input points to low dimensional latent variables. The \projection" mapping consists of an orthonormal matrix that is considered a priori unknown and needs to be inferred jointly with the GP parameters, conditioned on the available training data. The proposed Bayesian inference scheme relies on a two-step iterative algorithm that samples from the marginal posteriors of the GP parameters and the projection matrix respectively, both using Markov Chain Monte Carlo (MCMC) sampling. In order to take into account the orthogonality constraints imposed on the orthonormal projection matrix, a Geodesic Monte Carlo sampling algorithm is employed, that is suitable for exploiting probability measures on manifolds. We extend the proposed framework to multi-fidelity models using GPs including the scenarios of training multiple outputs together. We validate our framework on three synthetic problems with a known lower-dimensional subspace. The benefits of our proposed framework, are illustrated on the computationally challenging aerodynamic optimization of a last-stage blade for an industrial gas turbine, where we study the effect of an 85-dimensional shape parameterization of a three-dimensional airfoil on two output quantities of interest, specifically on the aerodynamic efficiency and the degree of reaction

42 ENGINEERING↗
DOE OSTI2019

Modeling Variable-Impedance, Magnetically Insulated, Transmission Lines

Coupling generator current to electron-beam loads and dynamic-inductance loads (z pinches) is greatly improved with low-inductance vacuum transmission lines. Typically, magnetically insulated transmission lines (MITLs) utilize nearly constant impedance geometries where the minimum impedance (anode-cathode gap) is limited by electron loss during the setup of magnetic insulation. Constant-impedance MITL designs are not optimized for low inductance (Zτ) when given a constraint on vacuum electron flow. We describe the design and the modeling of MITLs that have a nonconstant impedance. The baseline variable-impedance MITL designs are based on equilibrium vacuum-electron flow models [1] that are incorporated into the Screamer circuit code [2]. Such designs satisfy the MITL limits in the areal density of the loss current and have magnetically insulated flow that is stable everywhere along the MITL. Different MITL designs are then modeled analytically and with a 2-D particle-in-cell computer code in order to quantify subtle electron losses driven by changes to the vacuum impedance as a function of distance along the transmission line. We present a variable-impedance MITL design that delivers more current with a lower inductance than found in constant-impedance MITL designs.

47 OTHER INSTRUMENTATION↗
DOE OSTI2022

An Experimental and Theoretical Examination of Air Ingress Rates During Small- and Medium-Break Air Ingress Accidents

Here, air ingress measurements using the 1/20th-scaled Helium Air Ingress gas Reactor Experiment (HAIRE) facility show key geometric variables of interest and their effect on air ingress in small- and medium-sized breaks in High Temperature Gas cooled Reactors. These variables include but are not limited to break diameter, break angle, and break wall thickness. Differing wall thicknesses for the same break diameter can have order-of-magnitude changes to the air ingress rate, which is a key figure of merit in the air ingress accident scenario. Additionally, different break sizes can change the importance of the angle in the break scenario. With smaller breaks, the flow will not transition from intermittent flow, to countercurrent flow, to diffusive flow as the break rotates from vertically upward toward vertically downward. This would lead to less variability with smaller breaks, which in turn would make the accident scenario more predictable for smaller-sized breaks.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2015

Measurement of four-jet differential cross sections in √s = 8 TeV proton-proton collisions using the ATLAS detector

Differential cross sections for the production of at least four jets have been measured in proton-proton collisions at √s = 8 TeV at the Large Hadron Collider using the ATLAS detector. Events are selected if the four anti-k t R = 0.4 jets with the largest transverse momentum (p T ) within the rapidity range |y| < 2.8 are well separated (ΔR 4j min > 0.65), all have p T > 64 GeV, and include at least one jet with p T > 100 GeV. The dataset corresponds to an integrated luminosity of 20.3 fb -1 . As a result, the cross sections, corrected for detector effects, are compared to leading-order and next-to-leading-order calculations as a function of the jet momenta, invariant masses, minimum and maximum opening angles and other kinematic variables.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2018

Thermal infrared remote sensing in assessing groundwater and surface-water resources related to Hannukainen mining development site, northern Finland

Mining development sites occasionally host complicated aquifer systems with notable connections to natural surface water (SW) bodies. A low-altitude thermal infrared (TIR) imaging survey was conducted to identify hydraulic connections between aquifers and rivers and to map spatial surface temperature patterns along the subarctic rivers in the proximity of the Hannukainen mining development area, northern Finland. In addition to TIR data, stable isotopic compositions (δ{sup 18}O, δD) and dissolved silica concentrations were used as tracers to verify the observed groundwater (GW) discharge into the river system. Based on the TIR survey, notable GW discharge into the main river channel and its tributaries (61 km altogether) was observed and over 500 GW discharge sites were located. On the basis of the survey, the longitudinal temperature patterns of the studied rivers were found to be highly variable. Hydrological and hydrogeological information is crucial in planning and siting essential mining operations, such as tailing areas, in order to prevent any undesirable environmental impacts. The observed notable GW discharge was taken into consideration in the planning of the Hannukainen mining development area. The results of this study support the use of TIR imagery in GW–SW interaction and environmental studies in extensive and remote areas with special concerns for water-related issues but lacking the baseline research.

58 GEOSCIENCES↗
DOE OSTI2019

Exploratory analysis of high-resolution power interruption data reveals spatial and temporal heterogeneity in electric grid reliability

Modern grid monitoring equipment enables utilities to collect detailed records of power interruptions. Here, these data are aggregated to compute publicly reported metrics describing high-level characteristics of grid performance. The current work explores the depth of insights that can be gained from public data, and the implications of losing visibility into heterogeneity in grid performance through aggregation. We present an exploratory analysis examining three years of high-resolution power interruption data collected by archiving information posted in real-time on the public-facing website of a utility in the Western United States. We report on the size, frequency and duration of individual power interruptions, and on spatio-temporal variability in aggregate reliability metrics. Our results show that metrics of grid performance can vary spatially and temporally by orders of magnitude, revealing heterogeneity that is not evidenced in publicly reported metrics. We show that limited access to granular information presents a substantive barrier to conducting detailed policy analysis, and discuss how more widespread data access could help to answer questions that remain unanswered in the literature to date. Lastly, given open questions about whether grid performance is adequate to support societal needs, we recommend establishing pathways to make high-resolution power interruption data available to support policy research.

24 POWER TRANSMISSION AND DISTRIBUTION↗
DOE OSTI2022

Species- and element-specific patterns of metal flux from contaminated wetlands versus metals shed with exuviae in emerging dragonflies

Dragonfly adults and their aquatic immature stages are important parts of food webs and provide a link between aquatic and terrestrial components. During emergence, contaminants can be exported into terrestrial food webs as immature adults fly away or be shed with their exuviae and remain in the wetland. Our previous work established metals accumulating in dragonfly nymphs throughout a contaminated constructed wetland designed to regulate pH and sequester trace metals from an industrial effluent line. In this paper we evaluated the concentration and mass of metals leaving the wetland in flying emergents versus remaining in the wetland with the shed exuviae in 10 species of dragonflies belonging to 8 genera. Nine elements (Cu, Zn, Cd, Mn, V, Mg, Fe, Al, Pb) were evaluated that include essential and nonessential elements as well as trace and major metals. Metal concentrations in the emergent body and exuviae can differ by orders of magnitude. Aluminum, Fe, Mn, and Pb were largely shed in the exuviae. Vanadium and Cd were more variable among species but also tended to be shed with the exuviae. In contrast, Cu, Zn, and Mg showed a higher tendency to leave the wetland with an emerging dragonfly. Metals shed in dragonfly exuviae can moderate the transport of metals from contaminated wetlands. Taxonomic- and metal-specific variability in daily metal flux from the wetland depended upon concentration accumulated, individual body mass, and number of individuals emerging, with each factor's relative importance often differing among species. This illustrates the importance of evaluating the mass of metals in an individual and not only concentrations. Furthermore, differences in numbers of each species emerging will magnify differences in individual metal flux when calculating community metal flux. A better understanding of the variability of metal accumulation in nymphs/larvae and metal shedding during metamorphosis among both metals and species is needed.

54 ENVIRONMENTAL SCIENCES↗